Heat exchanger

ABSTRACT

A heat exchanger, in which louver wall surfaces ( 3   c ) are twisted at a predetermined angle (θ1) with respect to a plurality of flat portions ( 3   a ) of fins ( 3 ) and an inter-louver path ( 5 ) is formed between the adjacent louver wall surfaces ( 3   c ), is disclosed. The center points ( 3   d ) of some louver wall surfaces ( 31   c ) are displaced from the center points ( 3   d ) of the other louver wall surfaces ( 32   c ) along the cooling water flow direction (X 1 ). As a result, the real louver pitch height (HLP) is increased beyond the louver pitch heights (HLP1, HLP2) of the louver wall surfaces ( 31   c   , 32   c ), respectively. Even in the case where the louver width (L) is reduced, therefore, the cooling air can be caught by the louver wall surfaces ( 3   c ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a heat exchanger effectively applicable to a radiator for exchanging heat between the cooling water of an internal combustion engine and the air.

2. Description of the Related Art

In a conventional heat exchanger, the fins have louver wall surfaces of which the forward end effectively improves the heat transfer rate. By tilting the louver wall surfaces, at a predetermined angle to flat portions, the cooling air flow is changed and introduced to a path between adjacent louver wall surfaces (inter-louver path), thereby improving the heat transfer rate of the fins (Japanese Unexamined Patent Publication No. 2003-83690).

SUMMARY OF THE INVENTION

In the conventional heat exchanger described above, shortening of the louver width to improve the performance reduces the louver pitch height (the size of the louver wall surface in the cooling water flow direction X1), and therefore the cooling air cannot be easily caught by the louver wall surfaces. As a result, the cooling air cannot be introduced to the inter-louver path. In spite of an improved effect at the forward end, the heat transfer rate of the fins cannot be improved.

In view of the above-mentioned fact, the object of this invention is to provide a heat exchanger in which the cooling air can be easily caught by the louver wall surfaces even with a shorter louver width.

In order to achieve the object described above, according to one aspect of this invention, there is provided a heat exchanger comprising a plurality of tubes (2) with an internal fluid flowing therein and stacked in the direction perpendicular to the direction (X1) of the internal fluid flow, and a plurality of fins (3) arranged between the tubes (2) to increase the heat transfer area in contact with an external fluid flowing between the tubes (2), wherein the fins (3) have a plurality of flat portions (3 a) substantially parallel to the direction (X2) of the external fluid flow, and a plurality of louver wall surfaces (3 c), twisted at a predetermined angle (θ1) to the flat portions (3 a), are formed on the flat portions (3 a) along the direction (X2) of the external fluid flow, and wherein the plurality of the louver wall surfaces (3 c) include at least a louver wall surface (31 c) having the center point (3 d) thereof along the louver width (X4) displaced from the center point (3 d) of the other louver wall surfaces (32 c) in the direction (X1) of the internal fluid flow.

With this configuration, the louver pitch height HLP in real terms is increased and, even when the louver width is shortened, the cooling air can be caught by the louver wall surfaces. Therefore, the cooling air can be positively introduced to the inter-louver path, and the heat transfer rate of the fins can be improved.

According to another aspect of the invention, there is provided a heat exchanger wherein a twisted portion, (3 e) where each flat portion (3 a) and each louver wall surface (3 c) cross each other as viewed along the fin height (X3), is displaced from the center point (3 d) in the direction (X4) along the louver width of the louver wall surface (3 c).

According to still another aspect of the invention, there is provided a heat exchanger comprising a plurality of tubes (2) with an internal fluid flowing therein and stacked in the direction perpendicular to the direction (X1) of the internal fluid flow, and a plurality of fins (3) arranged between the tubes (2) to increase the heat transfer area in contact with an external fluid flowing between the tubes (2), wherein the fins (3) have a plurality of flat portions (3 a) substantially parallel to the direction (X2) of the external fluid flow, and a plurality of louver wall surfaces (3 c) twisted at a predetermined angle (θ1) to the flat portions (3 a) are formed on the flat portions (3 a) along the direction (X2) of the external fluid flow, and wherein the plurality of the louver wall surfaces (3 c) include at least a louver wall surface (31 c) displaced from the other louver wall surfaces (32 c) in the direction (X1) of the internal fluid flow and, as viewed from the direction (X2) of the external fluid flow, the louver wall surface (31 c) and the other louver wall surfaces (32 c) are partially superposed, one on the other.

With this configuration, the real louver pitch height HLP is increased, and even when the louver width is shortened, the cooling air can be caught by the louver wall surfaces. Thus, the cooling air can be positively introduced to the inter-louver path for an improved heat transfer rate of the fins.

According to yet another aspect of the invention, there is provided a heat exchanger wherein the plurality of the louver wall surfaces (3 c) include at least a louver wall surface (31 c) arranged alternately with the other louver wall surfaces (32 c) along the direction (X2) of the external fluid flow.

According to a further aspect of the invention, there is provided a heat exchanger comprising a plurality of tubes (2) with an internal fluid flowing therein and stacked in the direction perpendicular to the direction (X1) of an internal fluid flow, and a plurality of fins (3) arranged between the tubes (2) to increase the heat transfer area in contact with the external fluid flowing between the tubes (2), wherein the fins (3) have a plurality of flat portions (3 a) substantially parallel to the direction (X2) of the external fluid flow, and a plurality of louver wall surfaces (3 c) twisted at a predetermined angle (θ1) to the flat portions (3 a) are formed on the flat portions (3 a) along the direction (X2) of the external fluid flow, and wherein a plurality of different louver pitches (LP1, LP2) are set.

With this configuration, the real louver pitch height HLP is increased and, even when the louver width is shortened, the cooling air can be caught by the louver wall surfaces. Thus, the cooling air can be positively introduced to the inter-louver path for an improved heat transfer rate of the fins.

According to a still further aspect of the invention, there is provided a heat exchanger wherein the short louver pitch (LP1) and the long louver pitch (LP2) are alternately set along the direction (X2) of the external fluid flow.

According to a yet further aspect of the invention, there is provided a heat exchanger wherein the fins (3) are corrugated and include a plurality of flat portions (3 a) arranged along the direction (X1) of the internal fluid flow and a plurality of curved portions (3 b) each connecting the adjacent flat portions (3 a).

The reference numerals in the parentheses attached to each means above indicate the correspondence with specific means described in the embodiments below.

The present invention may be more fully understood from the description of preferred embodiments of the invention, as set forth below, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a front view of a heat exchanger according to a first embodiment of the invention.

FIG. 1B is an enlarged view of a portion A in FIG. 1A.

FIG. 2A is a partly cutaway perspective view of fins 3 shown in FIG. 1.

FIG. 2B is an enlarged view of a portion B shown in FIG. 2A.

FIG. 3 is a perspective view of the fins 3 of FIG. 1B as seen in a direction different from FIG. 2A.

FIG. 4 is a side view of the fins 3 of FIG. 1B as seen from the direction X3 along the fin height.

FIG. 5 is a sectional view of the fins 3 of FIG. 1B seen from the direction X3 along the fin height.

FIG. 6A is a sectional view schematically showing the fins 3 of FIG. 1B as seen from the direction X3 along the fin height.

FIG. 6B is an enlarged view of a portion C in FIG. 6A.

FIG. 7 is a sectional view schematically showing the fins 3 of the heat exchanger, according to a second embodiment of the invention, as seen from the direction X3 along the fin height.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A heat exchanger according to a first embodiment of the invention is used as a radiator for cooling the cooling water of a vehicle engine (internal combustion engine) by exchanging heat between the cooling water and the air. FIG. 1A is a front view of a heat exchanger according to a first embodiment of the invention. FIG. 1B is an enlarged view of a portion A in FIG. 1A. FIG. 2A is a partly cutaway perspective view of fins 3 shown in FIG. 1. FIG. 2B is an enlarged view of a portion B shown in FIG. 2A. FIG. 3 is a perspective view of the fins 3 of FIG. 1B as seen in a direction different from FIG. 2A. FIG. 4 is a side view of the fins 3 of FIG. 1B seen from the direction X3 along the fin height. FIG. 5 is a sectional view of the fins 3 of FIG. 1B seen from the direction X3 along the fin height. FIG. 6A is a sectional view schematically showing the fins 3 of FIG. 1B as seen from the direction X3 along the fin height. FIG. 6B is an enlarged view of a portion C in FIG. 6A.

As shown in FIG. 1B, the radiator 1 includes a plurality of tubes 2 in which the engine cooling water flows, a plurality of corrugated fins 3 coupled to the outer surface of the tubes 2 and a pair of header tanks 4 arranged at the ends of the tubes 2 in the direction X1 of cooling water flow (hereinafter referred to as the cooling water flow direction X1) and communicating with each tube 2. The engine cooling water corresponds to the internal fluid according to the invention.

The tubes 2 are made of a metal (an aluminum alloy in this embodiment) and are internally formed with a cooling water path through which the cooling water flows. The tubes 2 are flat in shape. A multiplicity of the tubes 2 are stacked and fins 3 are arranged between each adjacent pair of the tubes 2, and the cooling air flows between each pair of adjacent tubes 2. The cooling air corresponds to the external fluid according to the invention.

The fins 3 promote the heat exchange between the cooling air and the cooling water by increasing the heat transfer area in contact with the cooling air. The fins 3 are formed of a metal (an aluminum alloy according to this embodiment), and fabricated by press or roller molding.

These fins 3, as shown in FIGS. 2 a to 6 b, include a flat portion 3 a having a flat surface substantially parallel to the direction in which the cooling air flows between the tubes 2 (hereinafter referred to as the air flow direction X2) and a curved portion 3 b for connecting adjacent flat portions 3 a. The fins 3 are formed in corrugated shape as viewed along the air flow direction X2. A plurality of the flat portions 3 a are arranged along the cooling water flow direction X1.

The air flow direction X2 is also orthogonal to the cooling water flow direction X1 and the direction X3 along the fin height FH. The fin height FH is a size corresponding to the height difference of the corrugated fins 3, i.e. the amplitude of the wave.

The flat portions 3 a are each formed integrally with the louver wall surface 3 c by cutting up the flat portions 3 a. A plurality of the louver wall surfaces 3 c are twisted at a predetermined angle θ1 (hereinafter referred to as the twist angle θ1) with respect to the flat portions 3 a as viewed from the fin height direction X3 and are formed on the flat portions 3 a along the air flow direction X2. The twist direction of the louver wall surface 3 c located upstream in the air flow direction X2 is different from the twist direction of the louver wall surface 3 c located downstream in the air flow direction X2. Inter-louver paths 5 are formed between adjacent louver wall surfaces 3 c. The louver wall surfaces 3 c are parallel to the direction in which the cooling air flows through the inter-louver paths 5.

Assuming that the direction along the twist angle θ1 is coincident with the direction X4 along the louver width, a part of the louver wall surfaces 31 c and the other louver wall surfaces 32 c have the respective center points 3 d, along the direction of louver width X4, which are displaced in the cooling water flow direction X1.

Also, assuming that the crossing point between the central portion along the thickness of each flat portion 3 a and the louver wall surface 3 c as viewed along the fin height direction X3 is a twist portion 3 e, the twist portion 3 e of a part of the louver wall surfaces 31 c and that of the other louver wall surfaces 32 c are displaced differently from the center point 3 d along the direction X4 of louver width.

In other words, a part of the plurality of the louver wall surfaces 31 c and the other louver wall surfaces 32 c are displaced differently displaced along the cooling water flow direction X1 and superposed one on the other only partly as viewed along the air flow direction X2. Also, the louver wall surface 31 c displaced in one cooling water flow direction X1 and the louver wall surface 32 c displaced in the other cooling water flow direction X1 are arranged alternately along the air flow direction X2.

In the case where the plurality of the louver wall surfaces 3 c are arranged in this way, the louver pitch, i.e. the inter-louver distance along the air flow direction X2 is such that the shorter louver pitch LP1 and the longer louver pitch LP2 are set alternately along the air flow direction X2.

According to this embodiment, the fins 3 are made of aluminum alloy, and have a twist angle θ1 of 30° and a thickness t of 0.05 mm. The length L in the direction X4 along the width of the louver wall surface 3 c (hereinafter referred to as the louver width L) is 0.5 mm. Of the whole louver width L, the width L1 of the short side of the twist portion 3 e is 0.2 mm, while the width L2 of the long side of the twist portion 3 e is 0.3 mm.

Next, the operation and effects of this embodiment are explained.

According to this embodiment, a part of the louver wall surfaces 31 c and the other louver wall surfaces 32 c have the center points 3 d displaced from each other along the cooling water flow direction X1. Assuming that the size of the louver wall surfaces 31 c, 32 c along the cooling water flow direction X1 are the louver pitch height HLP1, HLP2, respectively, therefore, the real louver pitch height HLP is larger than the louver pitch height HLP1, HLP2 of the louver wall surfaces 31 c, 32 c, respectively.

Even in the case where the louver width L is shortened, therefore, the cooling air can be caught by the louver wall surfaces 3 c. Thus, the cooling air is positively led to the inter-louver path 5 for an improved heat transfer rate of the fins 3.

Preferably, the twist angle θ1 is not less than 20° and the louver pitches LP1, LP2 not more than 1 mm. Assuming that the length corresponding to one cycle of the corrugated fins 3 is defined as a fin pitch FP, the value FP/HLP is desirably not more than 10.

Also, the positions of the center points 3 d of a part of the louver wall surfaces 31 c and the other louver wall surfaces 32 c may be displaced from each other in the cooling water flow direction X1 at any point along the direction X3 of the whole fin height, or only at a point corresponding to the substantial center along the fin height direction X3.

A second embodiment of the invention will be explained. FIG. 7 is a sectional view schematically showing the fins 3 of the heat exchanger according to the second embodiment as viewed from the fin height direction X3.

Unlike in the first embodiment in which the twist direction of the louver wall surfaces 3 c located upstream in the air flow direction X2 and the twist direction of the louver wall surfaces 3 c located downstream in the air flow direction X2 are different from each other, all the louver wall surfaces 3 c have the same twist direction as shown in FIG. 7 according to the second embodiment.

While the invention has been described by reference to specific embodiments chosen for purposes of illustration, it should be apparent that numerous modifications could be made thereto, by those skilled in the art, without departing from the basic concept and scope of the invention. 

1. A heat exchanger comprising: a plurality of tubes (2) with an internal fluid flowing therein and stacked in the direction perpendicular to the direction (X1) of the internal fluid flow; and a plurality of fins (3) arranged between the tubes (2) to increase the heat transfer area in contact with an external fluid flowing between the tubes (2); wherein the fins (3) have a plurality of flat portions (3 a) substantially parallel to the direction (X2) of the external fluid flow, and a plurality of louver wall surfaces (3 c) twisted at a predetermined angle (θ1) to the flat portions (3 a) are formed on the flat portions (3 a) along the direction (X2) of the external fluid flow, and wherein the plurality of the louver wall surfaces (3 c) include at least a louver wall surface (31 c) having the center point (3 d) thereof along the louver width (X4) displaced from the center point (3 d) of the other louver wall surfaces (32 c) in the direction (X1) of the internal fluid flow.
 2. A heat exchanger according to claim 1, wherein a twisted portion (3 e) where each flat portion (3 a) and each louver wall surface (3 c) cross each, other as viewed along the fin height (X3), is displaced from the center point (3 d) in the direction (X4) along the louver width of the louver wall surface (3 c).
 3. A heat exchanger comprising: a plurality of tubes (2) with an internal fluid flowing therein and stacked in the direction perpendicular to the direction (X1) of the internal fluid flow; and a plurality of fins (3) arranged between the tubes (2) to increase the heat transfer area in contact with an external fluid flowing between the tubes (2), wherein the fins (3) have a plurality of flat portions (3 a) substantially parallel to the direction (X2) of the external fluid flow, and a plurality of louver wall surfaces (3 c) twisted at a predetermined angle (θ1) to the flat portions (3 a), are formed on the flat portions (3 a) along the direction (X2) of the external fluid flow, and wherein the plurality of the louver wall surfaces (3 c) include at least a louver wall surface (31 c) displaced from the other louver wall surfaces (32 c) in the direction (X1) of the internal fluid flow and, as viewed from the direction (X2) of the external fluid flow, the louver wall surface (31 c) and the other louver wall surfaces (32 c) are partially superposed one on the other.
 4. A heat exchanger according to claim 3, wherein the plurality of the louver wall surfaces (3 c) include at least a louver wall surface (31 c) arranged alternately with the other louver wall surfaces (32 c) along the direction (X2) of the external fluid flow.
 5. A heat exchanger comprising: a plurality of tubes (2) with an internal fluid flowing therein and stacked in the direction perpendicular to the direction (X1) of the internal fluid flow; and a plurality of fins (3) arranged between the tubes (2) to increase the heat transfer area in contact with an external fluid flowing between the tubes (2), wherein the fins (3) have a plurality of flat portions (3 a) substantially parallel to the direction (X2) of the external fluid flow, and a plurality of louver wall surfaces (3 c) twisted at a predetermined angle (θ1) to the flat portions (3 a) are formed on the flat portions (3 a) along the direction (X2) of the external fluid flow, and wherein a plurality of different louver pitches (LP1, LP2) are set.
 6. A heat exchanger according to claim 5, wherein the short louver pitch (LP1) and the long louver pitch (LP2) are alternately set along the direction (X2) of the external fluid flow.
 7. A heat exchanger according to claim 1, wherein the fins (3) are corrugated and include a plurality of flat portions (3 a), arranged along the direction (X1) of the internal fluid flow, and a plurality of curved portions (3 b) each connecting the adjacent flat portions (3 a). 